Polymer Insulators and Coatings in the Cretan Power System. The 

Transmission Line Case

Dionisios PylarinosConsultant, Hellenic ElectricityDistribution Network Operator

S.A., Crete, Greece

Kiriakos SiderakisAssistant Professor, Technological & 

Educational Institute of CreteGreece

Emmanuel KoudoumasProfessor, Technological Educational Institute of Crete, Iraklion, Greece

Emmanuel ThalassinakisAssistant Director, Hellenic ElectricityDistribution Network Operator S.A., 

Crete, Greece

Problem?

a single insulator fault may “cost” more than the total purchase cost for all the insulators of the transmission line

e.g. in the 80’s: 32.5% of all TL faults -> pollution

• coastal development, rocky coast, strong winds, dry period (April‐October)• insulators suffer intense  pollution 

The Cretan Power System

Pollution problem

East‐West diversity• heavier rains in the western side provide natural cleaning• faults/100km:more than 10 times more in the east compared to the west

• several remedies employed over the years• significant reduction in the total number of faults decade after decade

Pollution Phenomenon• pollutants deposition• wetting (mist, dew, rain etc)• creation of a conductive film • leakage current (LC) on surface• dry bands ‐>  arcing• arc propagation • flashover

Also note that:• rain may also wash clean• different  behavior  in  case  of  silicone insulators  but  similar  during hydrophobicity  loss  periods  (also stress/pollution related)

Flashover at TALOSH.V. Test Station, 

Crete(www.talos‐ts.com)

Strong winds, rocky coast,dry period increased salt deposition (Crete)

Note that:

RemediesA. washing (heli from 1995)

RemediesB. RTV SIR coating(from 2004)

Remedies• RTV SIR coating used only for special cases in TLs of Crete• coating performed by HEDNO personnel• usually offline but in some cases (poles) also online

Atherinolakos-Sitia TL

problem solved: strong winds

Ierapetra-Atherinolakos TL

problem solved: clearance vs length of availabe SIRs

Iraklion 2-Linoperamata TL

problem solved: high failure rate

RemediesC. HTV SIR composites (2004) • new problems (e.g. lighter, big bird attacks etc)

Main concern:performance vs aging

Additional weights

large scale installation of SIRs: the new insulation strategy

HTV SIR installation• first installation (2004) in the most polluted and important line 

(Linoperamata‐Atherinolakos)• no pollution related faults• low installation cost (=4.7 years of washing), large profit• the performance of silicone insulators is linked with the accumulated stress…i.e. silicone insulators “age”• further research needed on diagnose and assessment of insulatoraging & performance

POLYDIAGNO research project• partners: HEDNO, TEIC and FORTH• EU & Greek national funds• budget slightly over 0.5 M Euros• aim: to define a diagnostic procedure to assess aging and condition of silicone insulators

Basic scheme: Remove insulators from the network (along with new)

Monitor the performance under lab and field stress

Identify patterns/indicators using material analysis techniques

Labs : TEI of Crete and FORTH

Field stress and monitoring: HEDNO High Voltage Test Station

Define diagnostic procedure

POLYDIAGNO research projectFirst Step: • remove insulators from the grid• consider year in service • consider site pollution severity• seven 150 kV towers selected• three insulators removed from each tower• from each 3: 

• one sent to labs (TEI‐FORTH)• two sent to the test station (HEDNO)

TALOS High Voltage Test Station• HEDNO test station in the premise of Linoperamata Substation• subjected to coastal and industrial pollution• three bays: 150kV post, 150 kV suspension, 21 kV post & suspension

21 kV

150 kV150 kV

150 kV

TALOS & POLYDIAGNO

POLYDIAGNO insulators

POLYDIAGNO

POLYDIAGNO

Weather monitoring

Live weather report at: http://talos-ts.com/index.php/live-weather-report

Leakage Current monitoring• general purpose DAQs employed• use of explosive fuses for protection• Hall current sensors• sensors and DAQs housed in cabinet• LAN connection to PC housed in control room

Lab evaluationA. Electrical Analysis• Inclined Plane Test (IEC 60587) (active)• Dynamic Drop Test (WG D1.14, 2010)• Corona (WG D1.14, 2010)B. Physical Analysis – Contact Angle

Scanning Electron Microscopy

C. Material Analysis Fourier Transform Infrared Spectroscopy

New Aged also consideredLaser Induced Fluorescence, Laser Induced Breakdown Sprectroscopy

Results (“byproducts”)• first pollution map of the island,  agrees with experience and adds some new info/perspectives1,2• refurbish HEDNO’s chemistry lab for NSDD measurements1,2• remove some aged insulators from the system (10‐21 years of service)

1 D. Pylarinos, K. Siderakis, I. Pellas, E. Thalassinakis, “Assessing Pollution of Outdoor Insulators in the Cretan Power System”, 18th International Conference onCircuits, Systems, Communications and Computers (CSCC 2014), Santorini,  Greece, July 17‐21, 2014. 

2 D. Pylarinos, K. Siderakis, N. Mavrikakis, E. Thalassinakis, "Mapping HV Insulators’ Pollution in the Mediterranean Island of Crete", 9th InternationalConference on Deregulated Electricity Market Issues in South Eastern Europe, Nicosia, Cyprus, 25‐26 September, 2014 

Results• establish correlation factors for pollution measurements between different profiles/materials3• document similar yet different performance between RTV coated and HTV SIR insulators of similar characteristics4• propose a revised pollution map for Crete5• propose and investigate potential aging indicators and assessment techniques for HTV SIR insulators6‐8• upgrade the leakage current monitoring set‐up in TALOS9

3 M. Dimitropoulou, D. Pylarinos, K. Siderakis, E. Thalassinakis, M. Danikas, "Comparative Pollution Field Measurements on Outdoor Insulators of DifferentMaterial and Design", Engineering, Technology & Applied Science Research, accepted for publication

4 D. Pylarinos, K. Siderakis, E. Thalassinakis,"Comparative Investigation of Silicone Rubber Composite and RTV Coated Glass Insulators Installed in CoastalOverhead Transmission Lines", IEEE Electrical Insulation Magazine, Vol. 31, No. 2, 2015 

5 M. Dimitropoulou, D. Pylarinos, K. Siderakis, E. Thalassinakis, M. Danikas, "Insulation coordination and pollution measurements in the island ofCrete", International Conference on the Properties and Applications of Dielectric Materials (ICPADM), 19‐22 July, 2015 Sydney, Australia (submitted) 

6 N. Mavrikakis, K.Siderakis, E. Koudoumas, " Assessment diagnostics of the functionality of composite insulators operating in the 150kV power network ofCrete", 30th Panhellenic Conference on Solid‐State Physics and Materials Science, Heraklion, Crete, Greece, 21‐24 September, 2014

7 N. Mavrikakis, K. Siderakis, D. Pylarinos, E. Koudoumas, "Assessment of Field Aged Composite Insulators Condition in Crete", 9th International Conference onDeregulated Electricity Market Issues in South Eastern Europe, Nicosia, Cyprus, 25‐26 September, 2014

8 N. Mavrikakis, K. Siderakis, P. N. Mikropoulos, "Laboratory Investigation on Hydrophobicity and Tracking Performance of Field Aged Composite Insulators", 49th International Universities' Power Engineering Conference (UPEC), 2‐5 September 2014, Cluj‐Napoca, Romania

9 D. Pylarinos, K. Siderakis, E. Thalassinakis, “R&D in TALOS High Voltage Test Station‐Assessing aging and performance of polymer insulators”, 13th International Conference on Circuits, Systems, Electronics, Control & Signal Processing (CSECS '14), Lisbon, Portugal, October 30‐November 1, 2014  

Conclusions Crete  provides  a  rather  interesting  case  study  for  outdoor 

insulation  due  to  coastal  development,  local  climate,  different actions taken over the years and isolation 

Experience  from  Crete  can  be  used  as  a  guide  for  similar systems/conditions

Several remedies employed over the years Significant improvement achieved (fault reduction) Insulation coordination (TL) in Crete: latest step: equip with HTV SIR POLYDIAGNO  research  project  aim:  to  propose  a  diagnostic 

procedure to assess the aging of polymer insulators Research partners are: HEDNO, TEI of Crete, FORTH and ENTEC Project in progress, results  accumulated and periodically published  Follow  the  project  at  www.talos‐ts.com and 

http://sinergasia.iesl.forth.gr/